1. Field of the Invention
The invention relates to a carrier for carrying shaped charges for use in an elongated perforating gun of the type generally used to perforate oil and gas wells. The invention also relates to the assembly of the carrier and the shaped charge, to the design of the shaped charge, and to methods of assembling carriers and shaped charges. The invention particularly pertains to the manner in which the shaped charge is held in place relative to the carrier of the perforating gun.
2. Description of the Prior Art
Perforating guns commonly used in wire line and tubing conveyed service operations for perforating an oil or gas well typically include an elongated cylindrical outer housing within which is received an elongated carrier which has a number of shaped charges in place in the carrier. The carrier is located relative to the housing so as to locate each of the shaped charges adjacent reduced thickness portions of the housing.
A number of techniques have been utilized for holding shaped charges within a carrier.
Lug and slot type connection means have been utilized as shown in U.S. Pat. No. 3,078,797 to Blair wherein the lugs of a shaped charge are inserted through an opening adjacent a carrier, and then the shaped charge is rotated to lock it in place relative to the carrier.
Also, wire-type carriers have been utilized wherein the shaped charge has spaced shoulders which receive the carrier wires therebetween, as shown in U.S. Pat. No. 3,636,875 to Dodson.
A number of different techniques have utilized shaped charges having shoulders which rest against a carrier, in combination with separate attachment means such as screws, clips or the like. These are seen for example in U.S. Pat. No. 4,326,462 to Garcia et al.; U.S. Pat. No. 4,479,556 to Stout et al.; U.S. Pat. No. 4,312,273 to Camp; U.S. Pat. No. 4,543,703 to Wetzel et al.; and U.S. Pat. No. 4,541,486 to Wetzel et al.
More recently, the assignee of the present invention has developed a system in which the carrier includes resilient tab means extending into openings for receiving the shaped charges. The resilient tab means frictionally engage the shaped charge as it is pushed into the opening and thereby hold the the shaped charge in place within the opening. Such structures are shown for example in U.S. application Ser. No. 651,201, filed Sept. 17, 1984; U.S. Pat. No. 4,609,057; and U.S. Pat. No. 4,621,396, all assigned to the assignee of the present invention.
From these various examples just discussed, it is seen that the prior art has long recognized the need for a reliable means for retaining shaped charges in place within the carrier of a perforating gun. The present invention provides a much improved, very economical, reliable, and easily assembled construction for the assembly of a shaped charge with a carrier.